Project Summary There may not be a more significant biological threat than the malevolent release of B. anthracis spores, the causative agent of anthrax disease, over a major metropolis. With the inhalational form approaching 90% mortality, and a spore that can remain infectious for years, protection against this deadly disease is critical. The U.S. anthrax vaccine (AVA) induces toxin-neutralizing protection in animal models. However, its composition is unknown, its immunogenicity is short-lived, and it does not protect against some strains of B. anthracis. Our preliminary data suggests vaccination with bacillus near-iron transporter (NEAT) proteins, which function to acquire and import host heme during infection, can protect mice against anthrax disease. In this application, we use our molecular understanding of NEAT protein function to make and test a novel vaccine composed of heme transporters. We hypothesize vaccination with bacillus NEAT proteins will lead to opsonophagocytic antibodies that target infecting bacilli, unlike the current licensed vaccine, and thus provide broad protection against anthrax disease. Aim 1: Determine the optimal parameters for an effective vaccine composed of heme transporters. In this aim, critical parameters needed to fully evaluate the effectiveness of this vaccine strategy are determined, including specificity, dose, duration, and the optimal adjuvant needed for maximal efficacy for preventing inhalational anthrax. Aim 2: Determine the mechanism of protection and the effectiveness against capsulated strains. In this aim, the molecular mechanism by which this vaccine is protective is determined, and its effectiveness against the most virulent, capsulated strains is assessed. Since NEAT proteins are conserved in every major genus of Gram-positive pathogenic bacteria, this work also has universal appeal for vaccine development against related species.